1. Iron phosphides as efficient electrocatalyst for hydrogen evolution and energy conversion : abstractSaim Emin, Takwa Chouki, 2021, published scientific conference contribution abstract Abstract: Transition metal phosphides have been demonstrated as outstanding multifunctional catalysts in a broad range of energy conversion technologies. We developed a solvothermal synthesis approach for iron phosphide electrocatalystsusing a low-cost phosphorus precursor.The synthetic protocol allows for the preparation of a Fe2P phase at 300°C and FeP phase at 350°C. The obtained compounds were coated on conductive substrates to prepare catalysts thin films. Here, we exploited different phases of iron phosphide as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) with an I−/I3− based electrolyte [2]. The solar-to-current conversion efficiency of the solar cells assembled with the Fe2P material reached 3.96±0.06%,which is comparable to the device assembled with a platinum (Pt) CE. In addition to DSSC
applications, the iron phosphides were used as electrocatalyst for H2 evolution (Fig. 1). To enhance the catalytic activities of obtained iron phosphide particles, heat-treatments were carried out at elevated temperatures.Annealing at 500°C induced structural changes in the samples: (i) Fe2P provided a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500°C). The electrocatalytic activities for H2 evolution of heat-treated catalysts were studied in 0.5 M sulfuric acid (H2SO4). The HER activities of the iron phosphide catalyst were found to be phase dependent. The lowest recorded overpotential of 110 mV at 10 mA cm−2 vs. a reversible hydrogen electrode was achieved with Fe2P/FeP−500°C catalyst. The developed procedure is an elegant approach to tune the composition of iron phosphide catalyst and control the morphology of particles.
Keywords: Iron phosphides
electrocatalyst
hydrogen evolution
energy conversion
Published in RUNG: 06.02.2023; Views: 981; Downloads: 0
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2. Electrocatalytic Hydrogen Evolution with Transition Metal Based Compounds : abstractSaim Emin, Takwa Chouki, Manel Machreki, 2021, published scientific conference contribution abstract Abstract: Electrocatalytic water splitting is one of the cleanest and sustainable way to generate hydrogen. Transition metal based electrocatalysts like iron phosphides (Fe2P, FeP), molybdenum diselenides (MoSe2), and tungsten carbides (W2C, WC) have unique advantages including competitive cost compared to platinum, controllable active sites, and electronic structures that could significantly enhance the hydrogen evolution reaction (HER). Here, we present a combination of approaches for preparing catalyst materials. As an elegant technique, colloidal synthesis was used to synthesize Mo and W nanoparticles. Combined with selenization and carbidation approaches at elevated temperature, it allowed to synthesize MoSe2, W2C, and WC thin films. The syntheses of Fe2P and FeP catalyst were achieved in one-stage using triphenylphosphine precursor. The obtained catalysts were applied in electrocatalytic HER studies.
Keywords: iron phosphides
molybdenum diselenide
tungtsen carbides
electrocatalysis
hydrogen evolution
Published in RUNG: 06.02.2023; Views: 980; Downloads: 0
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3. Electroreduction of Nitrogen to Ammonia at Iron Catalytic Sites Generated at Interfaces Utilizing Iron Phosphides and Heme-Type Complexes : article2022, original scientific article Abstract: There has been growing interest in the development of durable,
specific and reasonably efficient low-cost catalysts for nitrogen
(N2) electroreduction reaction, or nitrogen fixation, particularly in
aqueous solutions capable of producing ammonia under ambient,
or near ambient, conditions. The successful electrocatalytic
reduction of nitrogen (N2) and formation of NH3 in alkaline an
medium has been reported here using the Fe3P phase of iron
phosphide. Detection of in-situ formed product has been achieved
by probing the electrooxidation of NH3 to nitrogen (N2) using the
additional working electrode modified with Pt nanoparticles. On
mechanistic grounds, the iron (Fe0) sites seem to be electrocatalytic
active during the reduction of nitrogen. The iron sites can also be
generated within the phtalocyanine ring binding metal ions through
four inwardly projecting nitrogen centers. Furthermore,
horseradish peroxidase metalloenzyme, in which a large alpha-
helical protein binds heme as a redox cofactor, is capable of
inducing electroduction of N2.
Keywords: Electroreduction of Nitrogen to Ammonia
Iron Catalytic Sites
Iron Phosphides
Published in RUNG: 06.02.2023; Views: 788; Downloads: 0
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4. Synthesis and application of transition metal phosphide nanomaterials as electrocatalysts for water splitting and chemical transformations : dissertationTakwa Chouki, 2022, doctoral dissertation Abstract: In this thesis, we will focus on the solvothermal synthesis of iron phosphides (FeP, Fe2P) using triphenylphosphine (TPP) as an inexpensive and stable phosphorus source. The obtained iron phosphides were applied as electrocatalysts in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), Rhodamine B (RhB) degradation, Escherichia coli (E. coli) inactivation,
nitrates reduction reaction (NO3RR) to ammonia (NH3), and as counter electrodes in dye-sensitized solar cells (DSSCs). Detailed characterizations of catalysts were carried out to investigate the correlations between the material structure and catalytic activity.
The first part of the thesis gives an introduction to the topic which cover overview of literature about the use of transition metal phosphide as efficient electrocatalysts in water splitting studies, NO3RR to NH3 and DSSCs.
The second part is a description of the experimental methods.
The third part discusses the solvothermal synthesis of FeP and Fe2P catalysts using TPP precursor. The phase conversion of iron phosphides at elevated temperatures under reductive atmosphere was reported. Structural characterizations of the obtained materials were achieved using multiple techniques. The electrocatalytic activities of heat-treated iron phosphide films for HER were studied in acidic environment.
The fourth part discusses the use of Fe2P nanoparticles (NPs) for OER.
The fifth part outlines the use of Fe2P precatalyst in water treatment studies. Using a thin film of Fe2P precatalyst, RhB degradation and E. coli inactivation in the presence of in-situ generated reactive chlorine species were reported. Characterization of Fe2P electrocatalysts before and after the test was carried out using different techniques.
The sixth part shows for the first time the use of FeP and Fe2P as a noble metal-free electrocatalysts for NO3RR to NH3. In this chapter we will emphasize the nitrate reaction pathways, which are highly complex and poorly understood.
The seventh part demonstrates the use of FeP and Fe2P catalysts as robust and efficient counter electrodes in DSSCs.
Keywords: solvothermal synthesis, iron phosphides, electrocatalysis, HER, OER, RhB degradation, E. coli inactivation, NO3RR to NH3, DSSCs, dissertations
Published in RUNG: 29.08.2022; Views: 1798; Downloads: 96
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